With the advance of technologies, the bathtub equipment has been significantly improved. In most families, there is equipment for both shower and bathtub and can switch from one to the other. For the shower head, the water pressure is more important to increase the speed of the water flow to have a better result of showering. On the other hand, the bathtub needs a larger amount of water output (per unit time) to effectively reduce the time to fill the bathtub. In conventional bathtubs, the water channels inside the switch valve are symmetric, and the water outlet hole of the ceramic valve piece is only ¼ of the original size, so that the switch valve can only provide the function of switching the water flow, but cannot change the amount of water when switching to the shower head or bathtub. Therefore, the water flow is identical in both the shower head and the bathtub. It is disadvantageous that the flow speed of the shower head too weak, while the amount of water output is not enough to effectively fill the bathtub in a short period of time.